Voltage regulator



July 1. 1947- J. Mcc. B RUMBAUGH 2,423,368

VOLTAGE REGULATOR Filed Sept. 22, 1943 CSM l Gttorneg Patented July 1,1947 VOLTAGE REGULATOR John McCall Brnmbaugh, Lansdowne, Pa., assignorto Radio Corporation of America, a corporation ot Delaware ApplicationSeptember 22, 1943, Serial No. 503,588

6 Claims. (Cl. 171-119) l The instant invention relates generally tovoltage regulating devices and more particularly to a D.C. voltageregulator circuit for a source of filtered direct voltage whereinvariations in the 2 wherein a control voltage is derived from arelatively high impedance circuit, and said voltage is applied to varythe impedance of a thermlonic tube which is connected in series withcapacitive output voltage derived from the filter are sta- 5 reactanceand wherein both tube and capacitive bilized by varying the reactancepresented by the reactance are connected across the input of a filter tothe voltage source. filter network interposed between the voltageHeretofore, various circuits have been employed source and a loaddevice. A further object of for reducing voltage fluctuations resultingfrom the invention is to provide an improved method power line voltagesurges and load variations enof 'and means for regulating a source ofdirect countered in power circuits for supplying opervoltage whichincludes a smoothing filter netating voltages to thermionic tubeapparatus. work interposed between thevoltage source and One of thedisadvantages of known systems of a load circuit, wherein the outputvoltage devoltage regulating is that considerable voltage rived from thefilter network varies the ratio of drop is inherent in the voltageregulating circapacitive to inductive reactance presented by cuit,thereby necessitating appreciably higher the filter network to thevoltage source. An source voltage than is required for the loadciradditional object of the invention is to provide cuit. Thisdisadvantage is especially true in the an improved voltage regulator ofthe type dei types of'voltage regulation wherein compensating scribedwhich includes degenerative feedback shunt or series regulating circuitsare connected means to prevent circuit oscillation. intermediate thevoltage source and the load cir- The invention will be further describedby refcuit. y erence to the accompanying drawing of which the Theinstant invention contemplates a simple single figure is a schematiccircuit diagram of a regulating circuit responsive to the voltageouttypical embodiment thereof.

` put of a smoothing filter which is connected in- Referring to thedrawing. a source of alternattermediate the source of unregulatedvoltage and ing potential is applied to the input terminals I the loadcircuit. A relatively high impedance which are connected to the primarywinding 2 voltage divider selects a portion of the output of aconventional voltage step-up transformer' '3. voltage derived from thefilter and applies this The ends of a high voltage secondary winding 4voltage to a thermionic tube circuit which inof the transformer 3 areconnected to the two creases the anode-cathode impedance of a anodeelectrodes 5, 6, respectively, of a full wave thermionic tube inaccordance with increases in rectifier tube 1. The center terminal ofthe high the output voltage derived from the filter. The voltagesecondary winding 4 of the transformer anode-cathode circuit of thistube is connected 3 is connected to ground. The cathode 8 of the inseries with a capacitor, and the capacitor and full wave rectifier tube'I is energized by a low tube are connected across the input of thevoltage secondary winding 9 of the transformer smoothing filter network.The resulting effect is 3 and is connected to one terminal of a first todecrease the capacitive reactance, and increase inductive reactor II'I.The remaining terminal of the inductive reactance, presented by the lterthe first inductive reactor I3 is connected to one to the unregulatedpower source, which results 40 terminal of a second inductive reactor IIand to in appreciably stabilizing the output voltage deone terminal of afirst filter capacitor I2. The rived from the filter network. remainingterminal of the second inductive re- The invention will be describedherein with actor I I is connected to one of the positive outputreference to its application to a conventional fullterminals 30 and toone terminal of a second filter wavethermionic tube rectifier circuitwhich in- 40 capacitor I3. The remaining terminals of the cludes aconventional two stage low-pass lter first and second filter capacitorsI2, I31 respecnetwork. It should be understood, however, that tively,are connected to ground. the invention may be applied to other types ofOne terminal of a third filter capacitor I4, filtered power supplycircuits. which may have a value of the order of .5 micro- Among theobjects of the invention are to farad, is connected to the cathodeterminal of provide an improved voltage `regulating circuit the fullwave rectifier tube 1. The remaining for a source of direct voltage.Another object terminaliof the third filter capacitor Il is conof theinvention is to provide an improved nected to the anode of a firstcontrol thermionic method of and means for providing voltage regutube I5and to the cathode of a diode rectifier lation of a source of directvoltage wherein a tube I6. The anode of the diode rectifier tubesmoothing iilter network is interposed between I6 is connected toground. The cathode of the the voltage source and a load circuit.Another control thermionic tube I5 also is connected to object of theinvention is to provide an improved ground. method voi! and means forregulating the output A voltage divider, comprising a .plurality ofvoltage derived from a direct voltage source serially connected highresistors I1, I8, IIS, is

to the remaining grounded output terminal 2l.

One terminal of an anode coupling resistor 2i is connected to thepositive output terminal 88. 'I'he remaining terminal of the anodecoupling resistor 2l is connected to the anode and screen electrodes ofa second control thermionic tube The control electrode of the secondtherm- 22. ionic tube 22 is connected to an'adjustable terminal on thehigh resistor I8. The cathode electrode of the second thermionic tube 22is connected through a gaseous regulator tube 23,

which may be of the RCA type VR-150, to ground.

The cathode of the second control tube 22 is also l connected throughbleeder resistors 24, 24' to the positive output terminal 30, and isfurther connected through a pair of serially connected resistors 24, 25,to the control electrode of the first control thermionic tube I5. Aiirst by-pass capacitor 26 .is connected between the anode of the secondcontrol thermionic tube 22 and the common terminals of the seriallyconnected resistors 24 and 25.

In operation, the voltage control circuit pro-l vides extremely lowcurrent drain on the output of the filter network. An increase in theoutput voltage provides an increase in the voltage derived from theadjustable terminal of the high resistor i8, which decreases thenegative bias on.

the control electrode of the second thermionic control tube 22. Thecathode of the second control tube 22 is maintained at a substantiallyiixed voltage with respect to ground by means of the gaseous regulatortube 22. Therefore, an increase in the output voltage derived from thefilter network will increase the anode current of the second controltube 22 and decrease the voltage applied to the control electrode of therst thermionic control tube l5, thereby increasing the anode-tocathoderesistance of the iirst control tube. Since the first control tube l5and the serially-connected third filter capacitor I4 are connectedacross the input of the filter network, an increase in the internalresistance of the iirst control tube will effectively reduce thecapacitive reactance presented by the filter network to the rectliiedinput voltage source. The effect of reducing the input capacitivereactance of the filter network will be to decrease the output voltageapplied to the output terminals 30, 28. The diode rectiiier I6 providesa discharge path to ground for the third filter capacitor I4, in orderthat the capacitor may discharge into the load circuit.

Since the system inherently is regenerative, the second by-passcapacitor 29 and the feedback circuit comprising the serially-connectedcapacitor 21 and high resistor 28 are included to prevent oscillationduring the half cycle rectiii peaks of the rectified power source.

In a. typical circuit providing satisfactory voltage regulation and RCAtype 6L6 tube was selected for the iirst control tube, and RCA type 6AC7was selected for the second control tube, and a type 6X5 having itsanode electrodes connected reactors employed throughout the .circuitwill be determined by the frequency of the applied voltage source, thepermissible voltage ripple at the output terminals, and the particularthermionic tubes employed in the voltage regulator circuit.

Thus the invention described comprises an improved voltage regulatorcircuit for a source of unregulated direct voltage wherein extremely lowcurrent drain is required for the regulator circuit and whereinvariations in output voltage provide compensating variations in theratio of capacitive-to-inductive reactance of the network connected tothe unregulated power source.

I claim as my invention:

1. A voltage regulator comprising a source oi' voltage. a smoothingiilter network connected to said source, means for deriving a controlvoltage from the 'output voltage derived from said network, and meansincluding a capacitor and a thermionic tube serially connected acrosssaid filter network and responsive to said control voltage for varyingthe input shunt impedance presented by said fllter network to saidsource.

2. A voltage regulator comprising a source of voltage, a smoothingfilter network connected to said source, means including a voltagedivider for deriving a control voltage from the output voltage derivedfrom said network, and means including a capacitor and a thermionicdischarge tube serially connected across said filter network andresponsive to said control voltage for -varying the input shuntimpedance presented by said iilter network to said source.

3. A voltage regulator comprising a source of voltage, a smoothingiilter network connected to said source, means including a voltagedivider and a thermionic discharge tube connected to said voltagedivider for deriving a control voltage from the output voltage derivedfrom said network, and means including a capacitor and a secondthermionic tube serially connected across said filter network responsiveto said control voltage i'or varying the input impedance presented bysaid filter network to said source.

4. Apparatus of the type described in claim 3 including a degenerativefeedback circuit interposed between said thermlonic discharge tubes I orstabilizing said control voltage. y

5. Apparatus for the type described in claim 3 including a rectiiierproviding a discharge path forsaid capacitor.

6. A voltage regulator comprising a source of voltage, a smoothingiilter network connected to said source, means including a voltagedivider and a thermionic discharge tube connected to said voltagedivider for deriving a control voltage from the output voltage derivedfrom said network, and means including a capacitor and a secondthermionic tube serially connected across said filter network responsiveto said control voltage for varying the reactance presented by saidiilter network to said source.

JOHN McCALL BRUMIBAUGH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNrrED STATES PA'II'EN'rs Number Name Date 1,979,035 Hammond Oct. 30,1934 2,309,852 Lewis Feb. 2, 1943

